Go language practice: several methods to clear file contents

Go language has the following methods to clear file contents: Use the ioutil.Truncate function to truncate the file. Use the os.Truncate function to directly operate the file descriptor. Use the ftruncate system call to truncate the file directly.

Go language practice: Several methods of clearing file contents

Clearing file contents is a common operation in Go language. There are several ways to do this.

Use the ioutil.Truncate function

ioutil.Truncate function to truncate the file to the specified size. If the specified size is 0, the file is cleared.

package main

import (
    "fmt"
    "io/ioutil"
    "os"
)

func main() {
    f, err := os.OpenFile("test.txt", os.O_RDWR, 0644)
    if err != nil {
        fmt.Println(err)
        return
    }

    err = ioutil.Truncate("test.txt", 0)
    if err != nil {
        fmt.Println(err)
        return
    }

    fmt.Println("File emptied successfully.")
}

Use os.Truncate function

os.Truncate function with ioutil.Truncate Similar, but it operates directly on file descriptors.

package main

import (
    "fmt"
    "os"
)

func main() {
    f, err := os.OpenFile("test.txt", os.O_RDWR, 0644)
    if err != nil {
        fmt.Println(err)
        return
    }

    err = os.Truncate("test.txt", 0)
    if err != nil {
        fmt.Println(err)
        return
    }

    fmt.Println("File emptied successfully.")
}

Use ftruncate system call

ftruncate system call to truncate the file directly.

package main

import (
    "fmt"
    "os"
    "syscall"
)

func main() {
    f, err := os.OpenFile("test.txt", os.O_RDWR, 0644)
    if err != nil {
        fmt.Println(err)
        return
    }

    err = syscall.Ftruncate(int(f.Fd()), 0)
    if err != nil {
        fmt.Println(err)
        return
    }

    fmt.Println("File emptied successfully.")
}

Practical case

In the following practical case, we use the ioutil.Truncate function to clear a file:

package main

import (
    "fmt"
    "io/ioutil"
    "os"
)

func main() {
    // 打开一个现有文件
    f, err := os.OpenFile("test.txt", os.O_RDWR, 0644)
    if err != nil {
        fmt.Println(err)
        return
    }

    // 使用 ioutil.Truncate 清空文件
    err = ioutil.Truncate("test.txt", 0)
    if err != nil {
        fmt.Println(err)
        return
    }

    // 检查文件是否已清空
    fi, err := f.Stat()
    if err != nil {
        fmt.Println(err)
        return
    }

    if fi.Size() == 0 {
        fmt.Println("File emptied successfully.")
    } else {
        fmt.Println("File not emptied.")
    }
}

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